My cousin makes the best burgers, especially when grilled. Not everyone likes them as he often chops up peppers and sprinkles a little cayenne into the meat. That's before the jalapeno slices get added. The only change I'll make, when I can, is to use dijon mustard instead of regular, but that irritates him if he sees me do it, and might ask me if I couldn't afford Grey Poupon instead.
At a restaurant, I'm not so sure. I have a memory of Whataburger being good, but I was both tired and stoned at the time, and even if it was, it was over 20 years ago and is probably different today. I feel like I got an awesome, thick burger at some independent (no others in it). But all I can remember was that it was by a beach, I think maybe Venice, California.
I don't make a habit of fast food, but In-N-Out tempted me to make an exception because of their burgers and fries (and though it costs, they give you a lot more than the others so I think it's cheaper). I'd get something specific, I think (not sure) also with jalapenos, but I can't remember what. I went a few times when it was out of my way so they were doing something right.